Try Flubaroo Now

You'll be asked to authorize Flubaroo to run. Click the blue "Accept" button.

A new, blank spreadsheet will open with Flubaroo installed, and you'll see this message pop-up:

Copy the URL given (also linked here) into another browser window. In the spreadsheet that opens, copy all of the data. Then return to your new, blank spreadsheet and paste the data there (starting in cell A1). Your blank spreadsheet will now resemble the sample one.

Select "Grade Assignment" from the Flubaroo menu, and follow the instructions in the Overview.